1. Field of the Invention
The present invention relates to a navigation system which provides a display of a map image for the area around the position of a vehicle, various route guidance instructions and the like.
2. Description of the Related Art
Navigation systems for vehicles generally determine the present position of the vehicle, read map data in the vicinity thereof from a data storage medium such as CD, DVD or the like, and display the map data on a screen. On the screen, there is displayed a vehicle position mark showing the present position of the vehicle. As the vehicle is driven, the map data in the vicinity of the vehicle is scrolled, centering on the vehicle position mark, so that map information in the vicinity of the present position of the vehicle can be obtained all the time.
Moreover, most of the recent navigation systems for vehicles are provided with a route guidance function which makes it possible for a user to drive toward a desired destination without taking a wrong road. According to this route guidance function, a route connecting from a departure point to a destination with the smallest cost is automatically searched using map data by performing a simulation, such as a breadth-first search (BFS) method or a Dijkstra""s method, and the searched route is stored as a guidance route. Then, during driving, the guidance route is displayed on the screen by changing the color from that of other roads or drawing thicker on the map image, and displaying an enlarged map of the intersection into which the vehicle is advancing next or outputting spoken guidance instructions, to thereby guide the user to the destination.
In some roads or expressways in the United States, there is a lane referred to as carpool lane where only vehicles in which there are two or more passengers can travel. In the United States, since there is a relatively large number of vehicles in which there is no passenger other than the driver, this carpool lane is less congested compared to normal lanes, and vehicles in which two or more passengers are traveling can travel this lane to thereby reduce the traveling time considerably.
However, advancing into the carpool lane from the normal lane (hereinafter referred to as xe2x80x9cordinary lanexe2x80x9d) and leaving the carpool lane for the ordinary lane can only be performed at a predetermined advancing/leaving point. Accordingly, there arises the case where even if a driver of a vehicle traveling in the carpool lane knows that he/she is approaching the road exit, by means of a map image around the position of the vehicle displayed on a screen of the navigation system or by using the route guidance function, since there is no leaving point from the carpool lane to the ordinary lane, the driver cannot return to the ordinary lane and consequently passes the road exit. In particular, in expressways around large cities where there are a large number of ordinary lanes, such an inconvenience is likely to occur. To avoid such an inconvenience, it is better to return early to the ordinary lane from traveling in the carpool lane. However, if there are many leaving points before the expressway exit, returning early to the ordinary lane causes the problem that efficient driving cannot be performed. Such a problem may also occur not only in the case of driving in a carpool lane, but also in ordinary lanes where traffic between each other is restricted.
In view of the above situation, it is an object of the present invention to provide a navigation system which can make it possible to drive efficiently in lanes where advancing or leaving relative to other lanes is restricted.
To solve the above-described problems, the navigation system of the present invention stores map data including road information regarding a partial lane in a map data storage section, where a partial lane is one of a plurality of lanes constituting the road and advancing or leaving relative to other lanes is permitted only in a predetermined authorized section. The system performs a predetermined navigation operation by means of a navigation processing section, based on the position of the vehicle detected by a vehicle position detecting section and the map data stored in the map data storage section. The navigation operation is performed while taking into consideration restrictions regarding advancing and leaving relative to a partial lane in a plurality of lanes, thereby enabling efficient driving in a lane having such a restriction.
The above-described navigation processing section preferably judges the timing for performing a predetermined guidance notification regarding the authorized section, based on the position of the vehicle and the position of the above-described authorized section, and performs guidance notification by means of a guidance notification section at this timing. As a specific navigation operation, since guidance notification is performed regarding the above-described authorized section where advancing or leaving is permitted, partial lanes where advancing or leaving is restricted can be efficiently utilized by driving a vehicle while referring to this guidance notification.
Moreover, a user may set whether or not to use the above-described partial lane by means of a driving lane instruction section. Route search processing by a route search processing section included in the navigation processing section takes into consideration whether or not to use the partial lane depending on the setting made in the driving lane instruction section. As a specific navigation operation, by performing the route search processing using the above-described partial lane, the most efficient driving condition can be effectuated. Furthermore, since the availability of the above-described partial lane is optional, when there is a predetermined condition for its use, users can freely select whether they will drive in this partial lane or not depending on the situation at that time.
Specifically, the above-described partial lane may be the carpool lane designated in some roads in the United States. The availability of the carpool lane is determined according to the number of passengers in the vehicle, and the carpool lane is less congested compared to other lanes. However, advancing or leaving relative to an ordinary lane is possible only in a predetermined authorized section. Since various navigation operations can be performed with the road information regarding the carpool lane being included in the map data, efficient driving utilizing the carpool lane becomes possible.